The suspension of joint military exercises between South Korea and the United States last summer caused a "slight degradation" in the readiness of the allied forces, the nominee to head U.S. Forces Korea said Tuesday.

U.S. President Donald Trump announced after his Singapore summit with North Korean leader Kim Jong-un in June that some of the exercises would be suspended while negotiations to dismantle the North's nuclear weapons program were under way.

Some 28,500 American troops are stationed in the South to deter North Korean aggression after the 1950-53 Korean War ended in an armistice, not a peace treaty.

"I think the suspension of the exercise this past August and September I would say was prudent risk if we're willing to make the effort to change the relationship with the DPRK," U.S. Army Gen. Robert Abrams said during his confirmation hearing before the Senate Armed Services Committee, using the acronym for North Korea's official name, the Democratic People's Republic of Korea.

"Something has to adjust, in my view, to be able to start to build trust and confidence as we move forward in the relationship," he said.

But the general acknowledged that the forces' readiness was undermined to a small degree, something he said he was sure the outgoing commander, Gen. Vincent Brooks, addressed with alternative plans.

"I think that there was certainly degradation to the readiness of the force for the combined forces," Abrams said. "That's a key exercise to maintain continuity and to continue to practice our interoperability, and so there was a slight degradation."

The general also said North Korea's nuclear and ballistic missile programs continue to pose a "significant asymmetric and intercontinental threat," and planning for military exercises scheduled for next spring were ongoing.

Trump has questioned the need to keep troops in South Korea, citing the cost associated with their deployment.

Asked if the troops should be removed in the event that Kim gives up his nuclear and ballistic missile programs, Abrams voiced his reservations.

"Tactically, without any mention of any change in his conventional capability, I'd say that there would be a significant amount of risk tactically if (we) were to do that," he said.